The invention relates to a method for producing piezoelectric actuators with a multilayer structure of piezoelectric layers, for instance for a piezoelectric actuator for actuating a mechanical component such as a valve or the like and to an apparatus for performing the method.
It is well known to produce piezoelectric actuators with piezoelectric elements to utilize the so-called piezoelectric effect, these piezoelectric actuators being constructed of a material with a suitable crystalline structure. The construction of this piezoelectric actuator is done here in a plurality of layers (multilayer piezoelectric actuators), and the electrodes by way of which the electrical voltage is applied are each disposed between the layers. These piezoelectric multilayer actuators are produced conventionally by sheet casting, printing of the electrodes, and lamination. The printing, intermediate drying and lamination are so-called batch processes in this case. The piezoelectric actuators have several hundred laminate layers, and the contacting is done by means of two electrodes mounted on the sides. The inner electrodes must end in alternation in the interior of the actuator, because otherwise there would be a short circuit to the respective opposite pole. On these ends, mechanical stresses occur in operation, which can cause harmful cracks to develop, and the growth of these cracks during operation in the final analysis limits the service life of the piezoelectric actuator.
When an external electrical voltage is applied to the inner electrodes, a mechanical reaction of the piezoelectric element ensues, which as a function of the crystalline structure and the direction of the electrical voltage represents a pressure or tension in a predeterminable direction. Electrical charging of the piezoceramic stack causes these layers to expand or contract. The associated reciprocation of the piezoelectric stack can be used to switch a valve, for instance for controlling fuel metering in an internal combustion engine.